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【linux kernel 常用数据结构和设计模式】【数据结构 3】【模拟input子系统input_dev和input_handler之间的多对多关系】

news 2025/9/10 5:55:32

一、背景

上节内容我们介绍了内核中一对一、一对多、多对多的数据结构，本节我们参照内核 input 子系统来模拟 input 子系统里
input_dev ↔ input_handler 多对多关系，用中间对象 input_handle 把两者连起来。
加载模块后，可以在 dmesg 里看到设备和处理器的绑定关系。

二、驱动

2.1 code

// demo_input_m2m.c
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/list.h>struct my_input_dev;
struct my_input_handler;
struct my_input_handle;/* 中间关系对象 */
struct my_input_handle {struct my_input_dev *dev;struct my_input_handler *handler;struct list_head d_node; /* 挂到 dev->h_list */struct list_head h_node; /* 挂到 handler->h_list */
};/* 设备 */
struct my_input_dev {const char *name;struct list_head h_list; /* 所有关联的 handle */struct list_head node;   /* 挂到全局 dev_list */
};/* 处理器 */
struct my_input_handler {const char *name;struct list_head h_list; /* 所有关联的 handle */struct list_head node;   /* 挂到全局 handler_list */
};/* 全局链表 */
static LIST_HEAD(dev_list);
static LIST_HEAD(handler_list);/* 工具函数：创建 handle 并建立关联 */
static void connect_dev_handler(struct my_input_dev *dev,struct my_input_handler *handler)
{struct my_input_handle *handle;handle = kzalloc(sizeof(*handle), GFP_KERNEL);if (!handle)return;handle->dev = dev;handle->handler = handler;INIT_LIST_HEAD(&handle->d_node);INIT_LIST_HEAD(&handle->h_node);/* 双向挂接 */list_add(&handle->d_node, &dev->h_list);list_add(&handle->h_node, &handler->h_list);pr_info("Connect: dev=%s <-> handler=%s\n", dev->name, handler->name);
}/* 初始化 demo */
static int __init demo_init(void)
{struct my_input_dev *kbd, *mouse;struct my_input_handler *evdev, *mousedev;struct my_input_handle *h;pr_info("demo_input_m2m init\n");/* 创建设备 */kbd = kzalloc(sizeof(*kbd), GFP_KERNEL);mouse = kzalloc(sizeof(*mouse), GFP_KERNEL);kbd->name = "keyboard";mouse->name = "mouse";INIT_LIST_HEAD(&kbd->h_list);INIT_LIST_HEAD(&mouse->h_list);list_add(&kbd->node, &dev_list);list_add(&mouse->node, &dev_list);/* 创建 handler */evdev = kzalloc(sizeof(*evdev), GFP_KERNEL);mousedev = kzalloc(sizeof(*mousedev), GFP_KERNEL);evdev->name = "evdev";mousedev->name = "mousedev";INIT_LIST_HEAD(&evdev->h_list);INIT_LIST_HEAD(&mousedev->h_list);list_add(&evdev->node, &handler_list);list_add(&mousedev->node, &handler_list);/* 建立绑定关系 */connect_dev_handler(kbd, evdev);     // keyboard -> evdevconnect_dev_handler(kbd, mousedev);  // keyboard -> mousedevconnect_dev_handler(mouse, evdev);   // mouse -> evdev/* 打印绑定关系 */list_for_each_entry(kbd, &dev_list, node) {pr_info("Device %s bound to: ", kbd->name);list_for_each_entry(h, &kbd->h_list, d_node) {pr_cont("%s ", h->handler->name);}pr_cont("\n");}return 0;
}/* 清理 */
static void __exit demo_exit(void)
{struct my_input_dev *d, *d_tmp;struct my_input_handler *h, *h_tmp;struct my_input_handle *hdl, *hdl_tmp;/* 释放 handle */list_for_each_entry(d, &dev_list, node) {list_for_each_entry_safe(hdl, hdl_tmp, &d->h_list, d_node) {list_del(&hdl->d_node);list_del(&hdl->h_node);kfree(hdl);}}/* 释放 dev */list_for_each_entry_safe(d, d_tmp, &dev_list, node) {list_del(&d->node);kfree(d);}/* 释放 handler */list_for_each_entry_safe(h, h_tmp, &handler_list, node) {list_del(&h->node);kfree(h);}pr_info("demo_input_m2m exit\n");
}module_init(demo_init);
module_exit(demo_exit);MODULE_LICENSE("GPL");
MODULE_AUTHOR("leo demo");
MODULE_DESCRIPTION("Demo: input_dev <-> input_handler many-to-many");

2.2 允许

/test # insmod demo_input_m2m.ko 
[   30.580747] demo_input_m2m init
[   30.581018] Connect: dev=keyboard <-> handler=evdev
[   30.581140] Connect: dev=keyboard <-> handler=mousedev
[   30.581275] Connect: dev=mouse <-> handler=evdev
[   30.581404] Device mouse bound to: evdev 
[   30.581569] Device keyboard bound to: mousedev evdev 
/test # 
/test #